Systems and Methods for Tracking Diver Location

ABSTRACT

Systems and methods for tracking diver location in accordance with embodiments of the invention are disclosed. In one embodiment, a dive computer includes a processor, a pressure transducer connected to the processor, and clock circuitry connected to the processor, wherein the processor obtains water speed information using a flow measurement device that measures water speed when below water, measures a first piece of position information using a global position system receiver (GPS) that generates position information, generates depth and time information using the pressure transducer and the clock circuitry when the dive computer is below water, combines the first piece of position information, depth information, water speed information, and time information into a dive log, stores the dive log using a memory, and estimates a position of a diver using the first piece of position information, time, depth, and water speed information from the dive log when submerged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/170,871, filed Jul. 10, 2008, which is a divisional of U.S. patentapplication Ser. No. 11/264,290, filed Oct. 31, 2005 and now abandoned,which is a continuation application of U.S. patent application Ser. No.10/615,635, filed Jul. 8, 2003 and now U.S. Pat. No. 6,972,715, whichclaims priority of U.S. Provisional Application No. 60/394,982, filedJul. 8, 2002, the disclosures of which are hereby incorporated byreference in their entirety.

FIELD OF INVENTION

The present invention relates generally to underwater exploration andmore specifically to apparatus and techniques for determining locationduring a dive.

BACKGROUND OF THE INVENTION

The development of self-contained breathing systems has enabled humansto dive and remain underwater for several hours. The ability to remainunderwater for an extended period of time can enable divers to reachconsiderable depths and cover expansive distances in exploringunderwater terrain.

A problem commonly encountered by divers is an inability to accuratelylocate position underwater. Position is typically expressed in terms ofthree co-ordinates. The position of a diver underwater can be expressedin terms of a latitude, a longitude and a depth co-ordinate. Thelatitude and the longitude co-ordinates represent the latitude and thelongitude of a point on the surface of the water directly above thediver. The depth co-ordinate represents the depth of the diver below thesurface of the water. A dive computer similar to a ProPlus 2manufactured by Oceanic Worldwide of San Leandro, Calif. can be used totrack depth during a dive. However, depth alone is insufficient tolocate the position of a diver during a dive.

SUMMARY OF THE INVENTION

Systems and methods for tracking diver location in accordance withembodiments of the invention are disclosed. In one embodiment, a divecomputer includes a processor, a pressure transducer connected to theprocessor, and clock circuitry connected to the processor, wherein theprocessor obtains water speed information using a flow measurementdevice that measures water speed when below water, measures a firstpiece of position information using a global position system receiver(GPS) that generates position information, generates depth and timeinformation using the pressure transducer and the clock circuitry whenthe dive computer is below water, combines the first piece of positioninformation, depth information, water speed information, and timeinformation into a dive log, stores the dive log using a memory, andestimates a position of a diver using the first piece of positioninformation, time, depth, and water speed information from the dive logwhen the dive computer is submerged.

In another embodiment of the invention, the dive computer furtherincludes the flow measurement device.

In additional embodiment of the invention, the flow measurement deviceis located on the body of the diver and is connected to the divecomputer.

In yet another additional embodiment of the invention, the flowmeasurement device is connected to the dive computer using a wirelessconnection.

In still another additional embodiment of the invention the divecomputer further includes the GPS receiver.

In yet still another additional embodiment of the invention, the GPSreceiver is located on the body of the diver and is connected to thedive computer.

In yet another embodiment of the invention the GPS receiver obtains thefirst piece of position information when the dive computer is abovewater.

In still another embodiment of the invention, the GPS receiver isconnected to a buoy above water, the buoy includes an antenna, and theGPS receiver obtains position information using the antenna.

In yet still another embodiment of the invention the GPS receiverobtains position information when the dive computer is below water.

In yet another additional embodiment of the invention the processorcalculates the amount of time a diver can remain at a particular depthwithout the need for decompression stops.

In still another additional embodiment of the invention, the divecomputer further includes a temperature sensor and the processordetermines water temperature using the temperature sensor.

In yet still another additional embodiment of the invention, theprocessor calculates when a diver can safely board an airplane based onthe dive log.

In yet another embodiment of the invention, the memory includes aplurality of memory units and at least one of the plurality of memoryunits is removable from the dive computer.

In still another embodiment of the invention, the processor measures asecond piece of position information using the GPS receiver after thedive computer is above water after being below water and the processorestimates a position of a diver using the combined time, depth, andposition information from the dive log using the second piece ofposition information.

In yet still another embodiment of the invention, the second piece ofposition information is included in the dive log.

In yet another additional embodiment of the invention, the processorfurther determines a straight line distance between the start point ofthe dive and the position of the diver and calculates a speed of thedive computer based on the time information in the dive log and thedetermined straight line distance.

In still another additional embodiment of the invention, the flowmeasurement device is connected to an air tank.

In yet still another additional embodiment of the invention, the divecomputer further includes a compass that determines the direction thatthe compass is moving and the processor obtains direction informationfrom the compass.

In yet another embodiment of the invention, the processor combines thedirection information into the dive log.

In still another embodiment of the invention, the dive computer can beworn on the wrist of the diver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of a dive computerin accordance with practice of the present invention;

FIG. 2 is a flow chart illustrating a method of recording latitude,longitude, depth and time during a dive in accordance with practice ofthe present invention;

FIG. 3 is a flow chart illustrating a method of locating a point ofinterest using data recorded in accordance with practice of the presentinvention;

FIG. 4 is a schematic illustration of a dive computer including a buoyhaving a GPS receiver antenna that is connected to the dive computer viaa spool of communication cable;

FIG. 5 is a side view of a submerged diver equipped with a dive computerin accordance with the present invention including a buoy that isdeployed at the surface;

FIG. 6 is a flow chart illustrating a method of recording latitude,longitude, depth and time during a dive in accordance with practice ofthe present invention that ensures that an automatic measurement oflatitude, longitude and time is made as a dive is commenced;

FIG. 7 is a flow chart illustrating a method of recording locations thata diver considers important;

FIG. 8 is a flow chart illustrating a method of detecting speechcommands in accordance with practice of the present invention;

FIG. 9 is a schematic illustration of an embodiment of a dive computerin accordance with practice of the present invention that includes animpeller and a compass;

FIG. 10A is a side view of a diver equipped with an air tank including aregulator and using a dive computer that includes an impeller and acompass mounted on the first stage of the regulator in accordance withpractice of the present invention;

FIG. 10B is a side view of diver using a dive computer that includes animpeller and a compass that is hose mounted;

FIG. 10C is a side view of diver using a dive computer that includes animpeller and a compass that is wrist mountable;

FIG. 11 is a flow chart illustrating a method of recording latitude,longitude, depth, time, bearing and water speed during a dive inaccordance with practice of the present invention;

FIG. 11A is a flow chart illustrating a method of estimating the coursetaken by a diver based on GPS measurements and water speed, depth andbearing measurements recorded during the dive;

FIG. 12 is a schematic illustration of an embodiment of a dive computerin accordance with practice of the present invention that includes apressure transducer for measuring air pressure in an air tank; and

FIG. 13 is a flow chart illustrating a process for estimating the rangeof a diver using information concerning air time remaining and waterspeed.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, dive computers in accordance withpractice of the present invention are illustrated. The dive computersmake and record at least three significant sets of measurements, whichenable the estimation of the location of points of interest underwaterand the path traveled by a diver during a dive. The first set ofmeasurements typically includes measurements of latitude, longitude andtime immediately prior to the commencement of a dive. The second set ofmeasurements can be generated by periodically measuring depth and timeduring a dive. The third set of measurements can be compiled bymeasuring latitude, longitude and time immediately upon resurfacing froma dive. Following a dive, an estimation of location at a specified timeduring the dive using these three sets of measurements can be made byusing a number of techniques in accordance with practice of the presentinvention. In several embodiments, the accuracy of the estimation can beincreased by including measurements of speed and bearing in the secondset of measurements.

Turning now to FIG. 1, a dive computer in accordance with practice ofthe present invention is illustrated. The dive computer 10 includes aprocessor 12 that is connected to memory 14, a global positioning system(GPS) receiver 16, clock circuitry 18 and an input/output interface 20.The input/output interface 20 is connected to a number of devices thatcan be used to communicate with a user or other devices. In oneembodiment, these devices include a pressure transducer 22, a keypad 24,a display 26, a communications port 28 and a microphone 30. A digitalcamera 32 is also provided as an input device, however, the digitalcamera bypasses the microprocessor and is connected directly to thememory 14.

The processor 12 receives information from the GPS receiver 16, theclock circuitry 18 and the input/output interface 20 and selectivelystores the information in memory 14. In one embodiment, the processor isimplemented using a MSP430F149 manufactured by Texas InstrumentsIncorporated of Dallas, Tex. However, the processor could be implementedusing discrete logic components or several separate processing elementsthat share information.

The memory 14 can be used to store data logged by the dive computer 10,to temporarily store information during the performance of calculationsand to store software used to control the operation of the processor 12.The memory 14 need not be a single integrated circuit and can beconstructed from a number of integrated circuits having distinctproperties. In the illustrated embodiment, the memory 14 includesnon-volatile memory circuits 34 to store software for controlling theprocessor 12, manufacturer settings, user settings and calibration data.In addition, the memory 14 also includes a removable memory device 36that is used to store data logged during a dive such as images, a diveprofile, dive logs, GPS logs and/or audio recordings. One aspect ofusing a removable memory device is that individual dives can be loggedon separate removable memory devices and the removable memory devicesused as a method of storing the logged data remote from the divecomputer. In embodiments that use a MSP430F149 processor or equivalentprocessor device, the non-volatile memory included on the processor chipcan be used to implement the non-volatile memory circuits 34 and theremovable memory device can be implemented using a SDMB-128-768 128 MBMultiMedia Card manufactured by SanDisk of Sunnyvale, Calif. In otherembodiments, memory devices of various sizes, volatility and portabilitycan be used depending on the software requirements of the system and thedata logging requirements of the user. For example, the removable memorydevice can be replaced by a similar sized fixed memory device such as anAT2508N-1051-1.8 manufactured by Atmel Corporation of San Jose, Calif.or an equivalent memory device.

The GPS receiver 16 utilizes signals broadcast from satellites to makecalculations of latitude and longitude. The GPS receiver provides thelatitude and longitude information to the processor, which isresponsible for the processing and storage of the information. In oneembodiment, the GPS receiver is implemented using a GeoHelix-H GPSantenna manufactured by Sarantel Ltd. of Wellingborough, United Kingdom.In other embodiments, other GPS receiver technologies, such as anEmbedded 3.3V GPS Antenna in conjunction with an M-LocJ MPM module bothmanufactured by Trimble Navigation Limited of Sunnyvale, Calif., can beused that are capable of providing information to the processor that canbe used to generate latitude and longitude co-ordinates.

The clock circuitry 18 can be used to measure the passage of time.Typically the clock circuitry 18 will incorporate a quartz crystal thatis used to generate a periodic signal that can be observed in order tomeasure the passage of time. The clock circuitry 18 can also besynchronized with an external clock to enable time to be expressed inabsolute terms using a time, a day, a month and a year. In oneembodiment the clock circuitry is part of the MSP430F149 microcontrollerdescribed above. In other embodiments, the absolute time can be obtainedusing the GPS receiver 16.

The input/output interface 20 can be constructed from any variety ofwires, antennas, transmitters, receivers, connectors and buffers. Theconfiguration of the input/output interface 20 is dependent on theinput/output devices that are connected to the dive computer. In theembodiment shown in FIG. 1, the input/output devices include a pressuretransducer, a keypad, a display, a communications port and a microphone.In other embodiments, any other combination of input/output devices canbe connected to the dive computer via the input/output interface. In oneembodiment, the portion of the input/output interface connected to thepressure transducer includes a standard analog to digital converter. Inaddition, the input/output interface uses a display driver such as anS6B33A1 manufactured by Samsung of Seoul, South Korea to connect tosegment display 26 and a CS53L32A High Speed Analog to Digital convertermanufactured by Cirrus Logic, Inc. of Austin, Tex. to connect to themicrophone 30.

The pressure transducer 22 can be used to measure the pressure of thewater in which the dive computer is immersed. In one embodiment a17887.A Low Pressure Transducer manufactured by Pelagic Pressure Systemsof San Leandro, Calif. can be used to construct the pressure transducer22. In other embodiments, other circuits capable of generating anelectrical signal indicative of the water pressure in which the divecomputer is immersed can be used.

A keypad 24 is typically provided to enable the user to enterinformation concerning the dive or to direct the processor 12 to providethe user with information. In one embodiment, the keypad 24 includes oneor more buttons that can be used to tag the location of the user as apoint of interest. As will be explained in greater detail below, thetagged location can be subsequently retrieved from the memory 14 of thedive computer 10. In other embodiments, the keypad 24 can include one ormore buttons, toggles, joysticks or equivalent devices with which theuser can provide instructions to the processor 12.

A display 26 is typically provided to present information in a graphicalmanner to the user. Information that can be provided to the userincludes a recent GPS reading, depth and/or time. If the dive computer10 performs other functions, information relating to these functions canalso be communicated using the display 26.

One skilled in the art will appreciate that the connection of keypads 24and displays 26 to dive computers 10 is well known and any number ofpossible configurations, devices and circuitry could be used toestablish a connection between these devices and the processor 12.

The communications port 28 is provided to enable the transfer ofinformation between the dive computer 10 and other devices. In oneembodiment, the communications port 28 is an Integrated Low ProfileTransceiver Module IrDA standard such as the TFDU4100 manufactured byVishay Semiconductor, Inc. of Malvern, Pa. In other embodiments, otherwired or wireless connections and protocols can be used to communicatewith external devices. The transfer of information via thecommunications port 28 enables the movement of data and new softwarebetween the dive computer 10 and other devices. In one embodiment, diveinformation stored in the dive computer memory 14 can be loaded onto apersonal computer and stored, graphed or manipulated. In addition,information from a previous dive stored on an external device can beloaded into the memory 14 of the dive computer for reference during asubsequent dive or information stored within the dive computer can bemanipulated by external devices.

The microphone 30 is provided to enable the audio annotation of datalogged by the dive computer 10. The annotations can be made before,during or after a dive by making a digital recording of the words spokenby the user and associating them with a particular dive or withparticular tagged locations. In other embodiments, automatic speechrecognition could be used to generate textual annotations. The additionof automatic speech recognition technology would also enable the divecomputer to respond to audible instructions from the user. In oneembodiment, the microphone 30 can be a MAB-06A-B manufactured by StarMicronics Company, Ltd. of Edison, N.J. As described above, theinput/output interface 20 can include an analog-to-digital converter forconnection to the microphone. The analog-to-digital converter can samplethe analog signal generated by the microphone 30 and generate a digitalrepresentation of the analog signal. In one embodiment, theanalog-to-digital converter samples the signal from the microphone 30 ata rate of 8 kHz and uses 28 quantization levels to represent the signal.In other embodiments, other sampling rates and a different number ofquantization levels can be used as is appropriate.

In embodiments where automatic speech recognition is used, the processor12 or a discrete device in the input/output interface 20 can convert thedigital representations of the signals from the microphone 30 to text orcommands using hidden Markov models, neural networks, hybrid neuralnetwork/hidden Markov models or other speech modeling or recognitiontechniques. In one embodiment, speech recognition is performed using aRSC-4x Speech Recognition Microcontroller manufactured by Sensory, Inc.of Santa Clara, Calif.

The digital camera 32 is provided to enable the capture of images duringa dive and to enable the use of these images as part of a dive log ifdesired by the user. The digital camera can be implemented using a lensand an array of charge coupled devices both of which are containedwithin the waterproof dive computer housing. In one embodiment, thedigital camera is implemented using a MB86S02A CMOS sensor manufacturedby Fujitsu Microelectronics America, Inc. of Sunnyvale, Calif. tocapture image information and a MCF5307 Direct Memory Access Controllermanufactured by Motorola, Inc. of Schaumburg, Ill. to transfer the imageinformation directly to the memory 14. In other embodiments, anycircuitry capable of capturing a digital image can be used to obtainimage information and store it in memory either via direct memory accessor using the processor 12 in combination with the input/output interface22.

Other input or output devices in addition to those described above canbe connected to a dive computer in accordance with the presentinvention. In one embodiment speakers are connected to the input/outputinterface to enable the playback of recorded speech or to allow a diverto listen to music during a dive. In other embodiments, othercombinations of devices can be used to meet the information requirementsand data recording requirements of a diver during a dive.

Turning now to FIG. 2, a method 40 of recording information during adive that enables estimation of position in accordance with practice ofthe present invention is illustrated. The method includes taking (42) afirst GPS measurement, which is performed prior to descending (44) belowthe surface. Once below the surface, depth and time are periodicallymeasured (46). After ascending (48) to the surface, a second GPSmeasurement is taken (50).

If data is logged during a dive in accordance with the method 40, thenposition during the dive can be estimated. If the user tags a particularlocation during a dive as being of interest, then the user can use thedata logged in accordance with the method 40 shown in FIG. 2 tosubsequently locate the point of interest.

Turning now to FIG. 3, a method of locating a previously identifiedpoint of interest using data logged in accordance with practice of thepresent invention is illustrated. The method 60 includes calculating(62) the duration of the recorded dive, calculating (64) the time thatwas taken to reach the identified point of interest from the start pointof the dive and determining (66) a straight line ‘L’ between the startpoint of the dive and the end point of the dive. Once these functionshave been performed, a value ‘A’ is then calculated (68), which is equalto the length of the line ‘L’ multiplied by the time taken to reach thepoint of interest and divided by the duration of the dive. The value ‘A’is then used to locate (70) a point ‘P’ that is a distance ‘A’ from thestart point of the dive along the line ‘L’.

Once the point ‘P’ has been identified, a diver can travel (72) to thelatitude and longitude of point ‘P’ and commence a dive. The diver canthen enter the water and descend (74) to the recorded depth of the pointof interest. At this depth, the point of interest can be located bysearching (76) outwardly while attempting to maintain the recorded depthof the point of interest. The depth of a point of interest isparticularly important in relocating that point. The co-ordinatescalculated as the latitude and longitude of a point of interest usingdata collected by a dive computer in accordance with the practice of thepresent invention are simply estimates that place a diver in thevicinity of the point of interest. The knowledge of the depth at whichthe point of interest is located enables the diver to perform anexpanding search in the plane of that depth. Without this information, adiver could be forced to search in three dimensions instead of two. Theadvantages of knowing a depth co-ordinate are increased when the pointof interest forms part of the topography of the sea floor. A diver canrapidly locate such a point of interest by simply descending to therecorded depth of the point of interest and then searching outwardlyfrom the point of descent until a portion of the sea bed is encounteredat the recorded depth of the point of interest. By following thetopography of the sea bed at the depth of the point of interest, thediver has a high likelihood of rapidly relocating the point of interest.

The method 60 illustrated in FIG. 3 can use data recorded in accordancewith the method 40 shown in FIG. 2. The time recorded at the beginningof the dive and the time recorded at the end of the dive can be used tocalculate (62) the duration of the dive. Likewise, the time at thebeginning of the dive and the time recorded at the point of interest canbe used to calculate (64) the time taken to reach the point of interest.The latitude and longitude co-ordinates at the beginning of the dive andthe latitude and longitude co-ordinates at the end of the dive can beused to generate the line ‘L’ (68) and the times calculated above can beused to locate the estimated latitude and longitude of the point ofinterest as described above.

Other techniques can be used to locate a point of interest using datarecorded in accordance with practice of the present invention. In oneembodiment, the logged data can be used to return to a point of interestby commencing the second dive at the latitude and longitude of whicheverof the start and end points of the earlier dive was closest to the pointof interest. The diver can then travel towards the other of the startand end points. The point of interest can then be located by travelingin this direction at the recorded depth of the point of interest for atime approximating the time it took to travel to the point of interestduring the previous dive.

If a diver seeks to be able to return to a point of interest with a highdegree of accuracy on subsequent dives, then the diver is advised toascend to the surface at the point of interest. The dive computer 10 canthen make a GPS measurement and the diver can be confident thatreturning to the recorded latitude and longitude and descending to therecorded depth will enable rapid location of the point of interest.

An alternative to ascending to the surface is to use the dive computer10′ illustrated in FIG. 4 that includes a compass 70 and a GPS antenna72 mounted on a buoy 74, which is connected to the other components ofthe dive computer 75 via a spool 76 of communication cable 78. In otherembodiments, a wireless connection is used between the spool and theother components of the dive computer. When a diver wishes to take ameasurement of latitude and longitude at a point of interest, the buoyis released. At the surface, the antenna can receive the satellitesignals required to measure latitude and longitude. These signals arethen conveyed to the GPS receiver via the communications cable. In otherembodiments, additional components such as the entire GPS receiver canbe included in the buoy. In one embodiment the spool is an AR-05manufactured by Saekodive of Taiwan.

Displacement of the buoy relative to the position of the diver isillustrated in FIG. 5. The displacement of the buoy 74 relative to aposition “P” directly above the diver can be calculated usingPythagoras' theorem by measuring the length of communication cable 78released from the spool 76 and the depth of the diver. The length ofcommunication cable released can be measured using markings on the cable78 and entered in the dive computer manually or via voice command.Alternatively an external line counter could be used that communicatesto the processor of the dive computer via a wireless or wired link. Thedepth of the diver can be measured using the dive computer in the mannerdescribed above. The direction of the displacement can be determinedusing a compass bearing of the cable relative to the diver.

Embodiments of the dive computer in accordance with practice of thepresent invention can enable automatic recording of latitude andlongitude immediately prior to the dive computer 10 descending below thesurface of the water and immediately upon returning to the surface.Turning now to FIG. 6, a method in accordance with practice of thepresent invention for automatically recording the latitude, longitudeand time prior to commencing a dive and upon surfacing from a dive isillustrated. The method 90 includes making (92) and storing (94)measurements of latitude, longitude and time using a GPS receiver. Theprocess of measuring latitude, longitude and time with the GPS receiverand storing the values continues until the diver descends below thesurface and the answer to the decision (96) of whether the diver hasdescended below the surface becomes affirmative.

Once the diver is below the surface, measurements (98) of depth and timeare made and the measurements are recorded (100) in the memory of thedive computer. The measurement and recording of depth and time continuesfor as long as the diver remains below the surface and until the answerto the decision (102) of whether the diver has surfaced is affirmative.Once the diver has surfaced, a measurement (104) of latitude, longitudeand time is made and the measurement is recorded.

The method 90 described in FIG. 6 can ensure that the measurement storedat the commencement of the dive is the most recent measurement oflatitude, longitude and time that has been made by the GPS receiver 16and dive computer 10. In addition, the method 90 enables periodicmeasurement of depth and time during the dive and the rapid recording oflatitude, longitude and time when the diver resurfaces. In otherembodiments, the logging of latitude, longitude and time can beinitiated in response to user input.

The method 90 shown in FIG. 6 can be modified to enable the diver toidentify points of interest during the dive. Turning now to FIG. 7, amethod in accordance with the practice of the present invention ofidentifying points of interest during a dive is illustrated. The method110 is performed while the diver is under water. The method 110 cancommence with the measurement (112) of depth and time. Once ameasurement of depth and time has been made, the measurements arerecorded (114). Prior to making another measurement of depth and time, acheck is made (116) for any user input. If user input is detected, thenthe previous or next depth and time measurements are identified (118) asa point of interest.

In addition to identifying points of interest, it is desirable to beable to associate information with a point of interest. One advantageousmethod of providing inputs to a dive computer 10 is through the use of amicrophone, as is described above. Speech commands can be used tocontrol the function of the dive computer and speech can be eitherrecorded or converted to text in order to provide description orannotation to a point of interest. In embodiments where speech can berecorded, the recording of speech can be initiated by the pressing of abutton on the keypad 24 or by a voice command recognizable by the divecomputer. In one embodiment, the microphone is contained within a fullface mask enabling speech to be recorded underwater. In otherembodiments, more than one microphone is included so that a diver mayrecord speech using a first microphone and underwater sounds orenvironmental noise using a second microphone. In embodiments of thedive computer 10 that include a digital camera 32, one or more stillimages or a series of still images forming a video sequence can berecorded and associated with a point of interest.

Turning now to FIG. 8, a method in accordance with practice of thepresent invention is illustrated for responding to voice commands. Themethod 130 includes listening (132) for sound. Once sound is detected, adecision (134) is performed to determine if a “voice spotting” sound hasbeen detected. A “voice spotting” sound is a spoken word such as“computer” that can indicate that a user is preparing to speak a commandto a dive computer 10.

If the “voice spotting” sound is detected, then the method involveslistening (136) for a command. A dive computer 10 in accordance withpractice of the present invention will typically have a library ofcommands each requiring different responses from the processor 12. If asound is heard, then a decision (138) is performed to determine whetherthe sound corresponds to one of the commands recognized by the divecomputer 10. If a command is recognized, then a response is made (140)to the command. Once the response is complete, the process 130 returnsto listening (132) for sound to await the next command.

The method 130 described above uses a “voice spotting” technique. Inother embodiments, “voice spotting” is not required. The speechrecognition performed in “voice spotting” and detecting commands can beeither discrete or continuous recognition. The speech recognition canalso be either speaker dependent or speaker independent. In embodimentswhere annotation of points of interest can be performed, a speechcommand can cause the processor to begin digitally recording speech andto associate the recording with a particular point of interest. In otherembodiments, other forms of user input can be used to identify a pointof interest and to commence the digital recording of speech.Alternatively, a command can cause the processor to convert a passage ofspeech to text using speech recognition techniques and to associate thetext with a point of interest that can be identified using speechcommands or using an alternative user input technique.

As was observed above, latitude, longitude and time measurements made inaccordance with practice of the present invention can be used toestimate the latitude and longitude of a point of interest. The accuracyof this estimate can be effected by currents and the variation in thespeed at which the diver traveled during the dive. The accuracy of theestimated latitude and longitude of a point of interest can be improvedin accordance with the practice of the present invention by takingmeasurements of water speed and bearing as is discussed below.

A dive computer 10″ in accordance with the practice of the presentinvention including an impeller and a compass is illustrated in FIG. 9.The dive computer 10″ is similar to the dive computer 10 illustrated inFIG. 1, but with the addition that an impeller 150 and a compass 152 areconnected to the processor via the input/output interface. Impellers aredevices that generate signals that can be used to measure the flow rateof a liquid or the water speed of the dive computer. By attaching animpeller equipped dive computer to a diver, the output of the impellercan be used to measure the speed at which the diver is moving throughwater and the compass can be used to provide signals to the processorindicative of the direction in which the diver is moving. In oneembodiment, a 3000 impeller manufactured by Nielsen-Kellerman ofChester, Pa., in conjunction with a receiver coil connected to a counterthat can be used to implement the impeller and a HMC 1055 3-axismagnetic sensor manufactured by Honeywell International of Morristown,N.J., that can be used to implement the compass. In other embodimentsother types of flow measurement devices can be used to measure waterspeed.

A diver equipped with a dive computer in accordance with the presentinvention is illustrated in FIG. 10A. The dive computer 160 isimplemented as two discrete components 162 and 164. The first component162 is worn around the wrist of the diver and includes all of thecomponents of the dive computer 10″ illustrated in FIG. 10A except forthe impeller and the compass. The impeller and the compass are locatedin a second component 164 that is fixed to an air tank worn 166 by thediver. In the illustrated embodiment, the two components communicate viaa wireless communications link.

Typically, a diver is fully extended while swimming and fixing theimpeller in a direction parallel to the long axis 168 of the diver asthe diver swims provides an accurate measurement of the speed of thediver. In addition, mounting the compass so that the bearing measurementis made along a line parallel to the long axis of the diver also enablesan accurate measurement of bearing to be made. In order to ensure thatboth the impeller and compass are accurately aligned, it is desirablethat the impeller and the compass be fixed to maintain a positionrelative to the body of the diver throughout the dive. Therefore, in theembodiment illustrated in FIG. 10A the impeller and the compass arefixed to the air tank 166 and aligned to be approximately parallel tothe long axis 168 of the body of the diver, when the diver is fullyextended. In other embodiments, the impeller and the compass can befixed to other locations on the body or equipment of a diver. In otherembodiments, the compass and impeller are included in a single unit withthe other components of the dive computer and the position of theimpeller and the compass can be controlled by the diver. A diver can usesuch a dive computer in accordance with the present invention to takeinstantaneous current readings, to use instantaneous speed calculationsto calculate range based on air time remaining (see discussion below) orfor any other application where an instantaneous measurement of speedcan be useful. An example of a hose mounted dive computer 10″ includingan impeller and a compass is illustrated in FIG. 10B and an example ofwrist mountable dive computer 10″ including an impeller and a compass isillustrated in FIG. 10C.

A method of recording data in accordance with practice of the presentinvention is shown in FIG. 11. The method 40′ is similar to the method40 illustrated in FIG. 2, with the difference that the periodicmeasurements of depth and time are supplemented with periodicmeasurements of bearing and water speed.

Assuming there is insignificant current, the measurements obtained usingthe process illustrated in FIG. 11 provides a complete map of the coursetaken by a diver. The starting latitude and longitude locations providethe origin of the course and the path followed by the diver can bedetermined using the water speed, bearing, depth, and/or timeinformation. Factors such as drift current can be accounted for byscaling the course to ensure that it terminates at the location wherethe diver surfaced, as measured using the GPS receiver. This scaling canbe performed by the dive computer or by an external device thatmanipulates data provided by the dive computer.

In one embodiment, the process illustrated in FIG. 11A is used to adjustor scale the course obtained using recorded water speed and bearingmeasurements in response to the latitude and longitude measurementsobtained at the origin and termination of a dive. The process 170includes defining (172) a planar co-ordinate system at the origin of thedive using the co-ordinates x, y and z, where z represents the depthdimension. Calculating (174) position co-ordinates relative to theorigin of the path taken during the dive using the water speed, depthand bearing data. Determining (176) position co-ordinates of thetermination point of the dive based on the water speed, depth andbearing data. Determining (178) position co-ordinates of the terminationpoint of the dive based on the GPS receiver measurements of latitude andlongitude. Calculating (180) the scaling factors that the x and yco-ordinates of the termination point determined using the water speed,depth and bearing data must be multiplied by in order to obtain the xand y co-ordinates of the termination point determined using the GPSreceiver measurements of latitude and longitude. An estimate of the pathtaken during the dive is then obtained (182) by scaling the x and yco-ordinates of the points in the path determined using the recordedwater speed, depth and bearing measurements by the calculated scalingfactors. The estimated path can then be output (184) in terms oflatitude, longitude and depth by mapping the co-ordinates of the pathfrom the planar co-ordinate system that was defined relative to theorigin of the dive to latitude, longitude and depth co-ordinates.

An embodiment of a dive computer in accordance with the presentinvention that incorporates pressure transducers in order to measure airtime remaining is illustrated in FIG. 12. The dive computer 10″ includesa pressure transducer 200 that measures air pressure inside an air tank.In one embodiment, the pressure transducer 200 is implemented using ahigh pressure sensor such as an 18519.A manufactured by Pelagic PressureSystems of San Leandro, Calif. Air pressure measurements can beconverted into air time remaining statistics in accordance with themethods described in U.S. Pat. No. 4,586,136 to Lewis and U.S. Pat. No.6,543,444 to Lewis, both of which are incorporated herein by referencein its entirety.

Knowledge of the water speed of the diver and the change in air timeremaining can be used to generate useful information for a diver such asan estimation of the range that a diver can travel with the airremaining in the tanks of the diver. A process for calculating anestimation of range based on the air available to a diver is illustratedin FIG. 13. The process 220 includes recording speed over apredetermined period of time (222) and then calculating the averagespeed during that period of time (224). Once the average speed has beencalculated, the air time remaining is calculated (226). The air timeremaining calculation can be used in combination with the average speedcalculation to predict the range of the diver at current exertionlevels. In other embodiments, the air time remaining can be adjusted toreserve sufficient air to allow the diver to return to the surface fromthe depth at which the diver is located without significant risk ofdecompression sickness.

Although the foregoing embodiments are disclosed as typical, it will beunderstood that additional variations, substitutions and modificationscan be made to the system, as disclosed, without departing from thescope of the invention. Thus the present invention has been described byway of illustration and not limitation. For example, embodiments of theinvention can have GPS receivers adapted to be submerged in water thatare not connected to the processor. These embodiments log latitude,longitude and time information using the GPS receiver and separately logdepth and time information using a dive computer. The latitude,longitude and time information from the GPS receiver and the depth andtime information from the dive computer can be downloaded to the divecomputer or another computer and the methods described above can be usedto determine position. In addition, dive computers in accordance withthe present invention can perform functions performed by conventionaldive computers such as providing divers with information concerningdecompression limits or the amount of air remaining in a tank, however,it is not a limitation of the invention that the dive computer performthese functions or other functions typically associated withconventional dive computers. Other functions can also be performed bythe dive computer that are not traditionally associated with divecomputers such as functions normally attributed to personal digitalassistants (P.D.A.s) or other more powerful computing devices. Inaddition, dive computers in accordance with the present invention mayconsist of a conventional dive computer and a microphone and/or adigital camera and do not require the inclusion of a GPS receiver. Otherembodiments of dive computers in accordance with the present inventionmay also combine several of the features described above such as a buoyincluding a GPS antenna, a compass and an impeller. It is therefore tobe understood that the present invention can be practiced otherwise thanspecifically described without departing from the scope and spirit ofthe present invention. Thus, embodiments of the present invention shouldbe considered in all respects as illustrative and not restrictive.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents.

What is claimed is:
 1. A dive computer, comprising: a processor; apressure transducer connected to the processor; and clock circuitryconnected to the processor; wherein the processor: obtains water speedinformation using a flow measurement device that measures water speedwhen below water; measures a first piece of position information using aglobal position system receiver (GPS) that generates positioninformation; generates depth and time information using the pressuretransducer and the clock circuitry when the dive computer is belowwater; combines the first piece of position information, depthinformation, water speed information, and time information into a divelog; stores the dive log using a memory; and estimates a position of adiver using the first piece of position information, time, depth, andwater speed information from the dive log when the dive computer issubmerged.
 2. The dive computer of claim 1, wherein the dive computerfurther comprises the flow measurement device.
 3. The dive computer ofclaim 1, wherein the flow measurement device is located on the body ofthe diver and is connected to the dive computer.
 4. The dive computer ofclaim 3, wherein the flow measurement device is connected to the divecomputer using a wireless connection.
 5. The dive computer of claim 1,wherein the dive computer further comprises the GPS receiver.
 6. Thedive computer of claim 1, wherein the GPS receiver is located on thebody of the diver and is connected to the dive computer.
 7. The divecomputer of claim 1, wherein the GPS receiver obtains the first piece ofposition information when the dive computer is above water.
 8. The divecomputer of claim 1, wherein: the GPS receiver is connected to a buoyabove water; the buoy comprises an antenna; and the GPS receiver obtainsposition information using the antenna.
 9. The dive computer of claim 8,wherein the GPS receiver obtains position information when the divecomputer is below water.
 10. The dive computer of claim 1, wherein theprocessor calculates the amount of time a diver can remain at aparticular depth without the need for decompression stops.
 11. The divecomputer of claim 1, wherein: the dive computer further comprises atemperature sensor; and the processor determines water temperature usingthe temperature sensor.
 12. The dive computer of claim 1, wherein theprocessor calculates when a diver can safely board an airplane based onthe dive log.
 13. The dive computer of claim 1, wherein: the memorycomprises a plurality of memory units; and at least one of the pluralityof memory units is removable from the dive computer.
 14. The divecomputer of claim 1 wherein: the processor measures a second piece ofposition information using the GPS receiver after the dive computer isabove water after being below water; and the processor estimates aposition of a diver using the combined time, depth, and positioninformation from the dive log using the second piece of positioninformation.
 15. The dive computer of claim 14, wherein the second pieceof position information is included in the dive log.
 16. The divecomputer of claim 1, wherein the processor further: determines astraight line distance between the start point of the dive and theposition of the diver; and calculates a speed of the dive computer basedon the time information in the dive log and the determined straight linedistance.
 17. The dive computer of claim 1, wherein the flow measurementdevice is connected to an air tank.
 18. The dive computer of claim 1,wherein: the dive computer further comprises a compass that determinesthe direction that the compass is moving; and the processor obtainsdirection information from the compass.
 19. The dive computer of claim18, wherein the processor combines the direction information into thedive log.
 20. The dive computer of claim 1, wherein the dive computercan be worn on the wrist of the diver.